It’s a plague, a natural disaster, and a nightmare we have all experienced. Calf cramps that hurt so bad you don’t want to move, uncontrollable twitching in the thighs after a heavy squat or an embarrassing whole body tremble while trying to hold a plank. Muscle cramps, twitches, and shakes affect us all in one way or another. But what’s going on with the body when they happen? Why can’t you control your own body while trying to work out?!?! Well, the answer, as usual, is complicated yet very simple.
Exercise-Induced Muscle Cramps
Let’s start with a list of things that don’t help with cramping:
x Magnesium supplements
x Hydration status
x Sports drinks
x Shoe type
Muscle cramps happen for a wide variety of reasons, but for today we will focus in on the kind you get while exercising. It may surprise you to know that cramps do not happen because of dehydration or electrolyte loss/imbalance. Losses in fluids and electrolytes, plasma, blood volume, and body weight are similar in people who experience cramps and those who do not experience cramping (1). Ever get a cramp while doing calf raises? I certainly have, and I bet if you try to do calf raises until fatigue now, you will get a cramp regardless of your hydration status. The “until fatigue” part is important because that is why muscle cramps happen. The scientific way to put it is (2):
“The muscle spindle responds to length changes in the muscle. As length increases, the muscle spindle increases impulses to the agonist muscle to contract and decreases impulses to the antagonist muscle so it relaxes. The golgi tendon responds to length changes in the tendon and causes the agonist muscle to relax. Both work together to protect the muscle from over stretching. However, with fatigue, it has been noted that the muscle spindle activity increases while the golgi tendon activity decreases.“
In other words, your body thinks it’s going to injure itself through overtraining/overstimulation so it shuts down activity (3). The body does this by firing the nerves up to 150 electrical discharges every second (4). Aside from intensity of exercise, some causes of cramps include a family history of cramps, muscle damage, and heat illness (5).
– Static stretching of the muscle
– Acetic acid (found in pickle juice) to increase neurotransmitter inhibition to cramping muscles
– Maintaining safe body temperature via hydration and rest intervals
– Increasing total body strength to delay target muscle fatigue
– Avoiding stimulants
Shake Spasm and Twitch
Shakes, spasms, and twitching kind of come with the exercise territory. There are medical classifications for all of the following information; however, we will be talking about them from a benign exercise-induced standpoint. Shakes (tremors) are almost always harmless and will never be explained. They are a huge category of involuntary muscle activity, ranging from the trivial to the disastrous, from teeth chattering in the cold to the wobbles of Parkinson’s Disease. In healthy people, they are usually stress induced. So if your hands or legs are ever a bit shaky after a hard workout, it’s because our motor control systems are a bit delicate. This is why unwanted contractions are so common and yet usually meaningless. Muscle spasms are an informal, non-specific term often used to “explain” musculoskeletal pain. Back spasms specifically do not cause pain, but rather are caused by pain (8). Muscles are always turned on and active in healthy people, and there is no such thing as normal muscle tone which is why “feeling tight” really doesn’t mean too much. A “muscle spasm” is really just the body preparing for a task (9). Twitching/rippling (Myokymia) happens when your muscle gets fatigued, so the motor units of your muscle fibers, rather than firing all at once, alternate their contractions, like pistons. Essentially, there aren’t enough motor units available for smooth contraction, so muscles start to ripple and quiver with intense exertions.
A Riddle To Ponder
What’s caused by doing exercise, and what’s caused by not doing exercise? Cramps, shakes, spasms, and twitches! It all comes down to how you’re training. If you’re doing enough exercise, you will start to see these issue go away. If you increase your exercise intensity, you will see them return… temporarily. The body is a crazy mystical web of mysteries. We are still discovering a lot, but the more you learn, the more it seems like we only know the tip of the iceberg. So don’t be embarrassed if you shake like a leaf while holding a plank, it’s completely natural.
1. Schwellnus, M. P., Drew, N., & Collins, M. (2011). Increased running speed and previous cramps rather than dehydration or serum sodium changes predict exercise-associated muscle cramping: a prospective cohort study in 210 Ironman triathletes. British journal of sports medicine, 45(8), 650-656.
2. Miller, Kevin. The Neurological Evidence for Muscle Cramping. NATA Symposium, June 2011, New Orleans Convention Center, New Orleans, LA. Conference Presentation.
3. Nelson, N. L., & Churilla, J. R. (2016). A narrative review of exercise‐associated muscle cramps: Factors that contribute to neuromuscular fatigue and management implications. Muscle & nerve, 54(2), 177-185.
4. Miller, T. M., & Layzer, R. B. (2005). Muscle cramps. Muscle & nerve, 32(4), 431-442.
5. Shang, G., Collins, M., & Schwellnus, M. P. (2011). Factors associated with a self-reported history of exercise-associated muscle cramps in Ironman triathletes: a case–control study. Clinical Journal of Sport Medicine, 21(3), 204-210.
6. Miller, K. C., Mack, G. W., Knight, K. L., Hopkins, J. T., Draper, D. O., Fields, P. J., & Hunter, I. (2010). Reflex inhibition of electrically induced muscle cramps in hypohydrated humans. Med Sci Sports Exerc, 42(5), 953-961.
7. Casa, D. J., Armstrong, L. E., Hillman, S. K., Montain, S. J., Reiff, R. V., Rich, B. S., … & Stone, J. A. (2000). National Athletic Trainers’ Association position statement: fluid replacement for athletes. Journal of athletic training, 35(2), 212.
8. Friedmann, L. W. (1989). The myth of skeletal muscle spasm. American journal of physical medicine & rehabilitation, 68(5), 257.
9. Szeto, G. P. Y., Straker, L. M., & O’Sullivan, P. B. (2009). Neck–shoulder muscle activity in general and task-specific resting postures of symptomatic computer users with chronic neck pain. Manual Therapy, 14(3), 338-345.